If $x \circledcirc y = 2x^{2}-y^{2}$ and $x \oslash y = 3x+y$, find $(2 \circledcirc -1) \oslash 4$.
Explanation: First, find $2 \circledcirc -1$ $ 2 \circledcirc -1 = 2(2^{2})-(-1)^{2}$ $ \hphantom{2 \circledcirc -1} = 7$ Now, find $7 \oslash 4$ $ 7 \oslash 4 = (3)(7)+4$ $ \hphantom{7 \oslash 4} = 25$.